Recent technology trends in materials science indicate that the use of nanotechnology-enabled components and materials are gaining more appeal due to the enhanced (and sometimes even breakthrough) performance being exhibited. Functional nanomaterials exhibit many unique and often tunable physical and chemical properties that are different than those of their bulk counterparts. Developments have been recently made towards the fabrication of nanomaterials having well defined shape and dimensions involving either “top down” or “bottom up” fabrication strategies. “Top down” approaches involve cutting down larger structures into the desired shape with the desired dimensions (e.g. nanolithography). “Bottom up” strategies involve growing structures of the desired shape and dimensions from smaller building blocks (e.g. self-assembly). The latter is the preferred approach because it is much more efficient and bypasses the need for cost-intensive and energy-intensive fabrication processes.
Molecular self-assembly is a practical “bottom up” approach to arrive at nanostructured materials. In this approach, self-complementary molecules are designed as ‘building blocks’ with a specific size, shape and at least one functional group, to aggregate in an ordered manner. The resulting ensemble often possesses completely different properties than their smaller building subunits. However, the challenge of this approach is to design the appropriate molecular subunits that can assemble into useful nanostructures in a controlled manner such that the final desired size and shape can be achieved. Consequently, the modular use of hydrogen-bonding molecular building blocks is key to designing novel nanoscale supramolecular structures, non-covalent polymers, organogelators, and liquid crystals, that have useful properties for developing advanced functional materials such as for example adhesives, self-healing coatings, as well as many others.
Cyclic urea compounds that contain the benzimidazolone (BZI) functional group can self-assemble into hydrogen-bonded (H-bonded) dimer structures in the solid state resembling tapes or ribbons. These tape-like structures can vary in size and morphology depending on the type and position of functional substituents present on the benzimidazolones.
F. H. Herbstein et al., “Crystal and Molecular Structure of 1,3-dihydro-2H-benzimidazol-2-one (the solid state tautomer of 2-hydroxybenzimidazolone)”, Z. Kristallogr, vol. 173, p. 249-256 (1985), describes the crystal structure of 1,3-dihydro-2H-benzimidazol-2-one. Ribbons of antiparallel keto-tautomer molecules linked by a zigzag set of (N—H)—(O═C) donor-acceptor pairs of hydrogen bonds are formed. The ribbons are planar and lie in a herring-bone pattern.
G. M. Whitesides et al., “Engineering the Solid State with 2-Benzimidazolones”, J. Am. Chem. Soc., vol. 118, p. 4018-4029 (1996), describe the solid state structures of six 2-benzimidazolone derivatives, disubstituted in the 4 and 5 positions on the benzene ring. 2-Benzimidazolones having either methyl, chlorine, and bromine atoms at the 4 and 5 positions form tapes, which pack differently than 2-benzimidazolones with hydrogens in the same positions. In contrast, three-dimensional networks were formed from 2-benzimidazolones having fluorine or iodine substituents at both 4 and 5 positions.
E. F. Paulus, “Molecular and crystal structure of C. I. Pigment Red 208, 12514, n-Butyl-2-{2-oxo-2,3-dihydro-5-benzimidazolyl)-carbamoyl]-naphthylidenhydrazino}-benzoate (PV-Rot HF2B)”, Z. Kristal., vol. 160, p. 235-243 (1982) describes the crystal structure of azo-benzimidazolone Pigment Red 208. The pigment molecules are organized into tape-like structures. Each benzimidazolone group of the pigment molecules interacts with only one other benzimidazolone group from another neighboring pigment molecule to form a dimer assembly via a 2-point H-bonding interaction involving a carbonyl (C═O) acceptor and —(N—H) donor from each monomeric subunit. Each dimer is then further bound to two other dimers via two single-point H-bonding interactions between the benzimidazolone —(N—H) donor group and the 2-oxo-3-naphthylamido carbonyl group acceptor. The tapes have lipophilic edges and are further organized into layers in the crystal structure.
K. Hunger et al, “Über die Moleküund Kristallstruktur gelber Mono-“azo”-Pigmente”, Farbe & Lack, vol. 88, p. 453-458 (1982) describes the crystal structure of a yellow azo-benzimidazolone pigment. The pigment molecules are organized into tape-like structures. Each benzimidazolone group of one pigment molecule subunit interacts with only one benzimidazolone group from another neighboring pigment molecule subunit, to form a dimer assembly via a 2-point interaction involving a carbonyl (C═O) acceptor and —(N—H) donor from each half. Each dimer is then further bound to two other dimers via two single-point H-bonding interactions between the benzimidazolone —(N—H) donor and the acetoamido carbonyl group acceptor. The tapes are packed into a zig-zag type arrangement in the crystal structure.
J. van de Streek et al, “Structures of six industrial benzimidazolone pigments from laboratory powder diffraction data”, Acta Cryst., B65, p. 200-211 (2009) describes the crystal structures of six industrially produced benzimidazolone pigments modeled from X-ray powder diffraction data. The six industrial pigments exhibited five different tape-like hydrogen-bonded motifs.
Although hydrogen-bonded tape or ribbon structures have been observed in solid state X-ray crystal structures, it has not yet been demonstrated that benzimidazolones form “free-standing” nanostructures in solutions or dispersions. To our knowledge, the only microscopy studies that have been performed on self-assembled aggregates of benzimidazolone derivatives were by J. de Mendoza et al.
J. de Mendoza et al, “Resorcinarenes with 2-benzimdazolone bridges: self-aggregation, self-assembled dimeric capsules, and guest complexation”, Proc. Natl. Acad. Set. USA, 99, 4962-4966 (2002) describes the synthesis and self-assembly behavior tetra-2-benzimidazolone functionalized resorcinarene compounds having various pendant alkyl groups. Self-organized structures such as micron-sized vesicles and long fibers were formed depending on the nature and length of the four pendant carbon chains attached at the bottom of each resorcinarene platform. Solvophobic effects, van der Waals interactions, and the packing of alkyl chains drive the formation of these higher order supramolecular assemblies from the capsules, as compared to the extensive hydrogen-bonded chains involving the benzimidazolone functional groups for the compounds of the present invention.
The appropriate components and process aspects of each of the foregoing may be selected for the present disclosure in embodiments thereof, and the entire disclosure of the above-mentioned references are totally incorporated herein by reference.
However, there remains a need for new and improved nanotechnology-enabled components and materials, particularly those having self-complementary functional groups which can self-assemble readily by a “bottom up” fabrication strategy to produce well-defined nanostructures and potentially higher-order network structures, that can be useful and desirable properties in developing functional materials.